Conventional clothes dryers include a rotating drum into which textiles to be dried are placed. The textiles are dried by forcing heated air onto the wet laundry rotating with the drum. Moisture is removed along with the air exiting the dryer or via a condensed water duct.
Conventional clothes dryers have been controlled in various ways. The simplest of these is a timer that controls the duration of the drying cycle. When using a timer, the user places wet laundry inside the dryer and selects the duration for the drying process. The drying cycle then proceeds until the timer expires. Although this method is relatively simple, it is difficult to accurately estimate the length of time required to reach a desired final moisture level, or “dryness,” for every type of textile. If the cycle length is too short, the textiles will not be fully dry at the end of the cycle, and the user must initiate a another dryer cycle to finish the drying process. If, on the other hand, the cycle length is too long, the clothes may become “overdry,” resulting in premature textile degradation and/or damage, excess energy consumption, and an associated increase in energy costs.
Alternatively, various sensors that detect the “dryness” of the textiles within the dryer have been used to control the length of the dryer cycle. In that case, the dryer cycle runs until the sensor detect the final desired dryness level selected by the user. Such sensors are typically placed inside the dryer drum and come into contact with the textiles as they are tumbled through the dryer cycle. However, not all dryers, especially commercial dryers, are equipped with this type of sensor.
In addition, laundry additives are commonly applied to laundry during the dryer cycle. Certain of these laundry additives are designed to provide automatic dispensing of laundry products over multiple cycles. These products provide multiple-load functionality and minimal labor as they reduce the need to replace or refill a laundry product at the beginning of each cycle. One example of a multi-cycle laundry product includes solid blocks of fabric conditioner that are mounted in a carrier inside the drum of the dryer. The block provides moisture-controlled dispensing of the active ingredients on wet textiles as they tumble in the dryer. As soon as the textiles are dry, the product is no longer dispensed. The block dispenses the laundry product over multiple loads until is depleted, at which point the solid block of product must be replaced. Other examples of multi-cycle laundry products include dryer sheets, free-tumbling carriers of liquid fabric conditioner, and others.